The invention relates to an apparatus and method for axially aligning conduits to permit "tack" welding of the conduits prior to welding. In particular, the apparatus and method are particularly adapted to axially align conduits, irrespective of curvature, wall thicknesses and respective diameters of the conduits to be welded.
In welding two conduits together in end-to-end relation it is preferable to align the conduits axially to ensure a good quality, even weld. Such axial alignment is relatively easily achieved where the conduits to be joined are of the same diameter, have the same wall thickness and are straight at the end portions to be joined. However, such axial alignment is difficult to achieve when the conduits are curved as in the case of elbows, or where the wall thickness or outside diameter of the conduits are different as in the case of conduits supplied by different countries.
Previously, the alignment of curved conduits or conduits with differing wall thicknesses or outside diameters was performed by welding lugs onto respective end portions of the conduits to be joined and providing jacking bolts which could be selectively tightened to align the conduits. The joint could then be "tacked" and the jacking bolts removed and the lugs cut off to permit full welding of the entire joint. This however requires the complicated step of welding the lugs onto the conduits and then cutting the lugs off and grinding smooth the outside surfaces of the conduits. This can be very time consuming and in some cases is difficult to do due to space limitations in the proximity of the conduits. In addition, some types of steel such as Chrome steel cannot have lugs welded thereto.
Other inventors have sought to solve the problem of aligning conduits, however, they have addressed the problem of aligning straight conduits or conduits having a mitred joint. For instance U.S. Pat. No. 3,422,519 to Fehlman discloses a lineup clamp for pipe. However the surfaces for contacting the end portions of the pipe are spaced relatively far apart which might render the device difficult to use on curved portions of pipe.
U.S. Pat. No. 3,920,232 to Clark discloses an apparatus for aligning pipe ends which uses a hydraulic ram acting on a pipe in a circular cradle to align two pipes to be joined together. The apparatus thus appears to be intended for use with pipes of a specific diameter and of the same outside diameter and wall thickness.
U.S. Pat. No. 3,467,295 to Watson discloses a clamping means for pipes and fittings which has a first pipe contact member and an extending arm having a screw member acting as a second pipe contacting member. Considerable leverage is applied to the extending arm to provide sufficient force on the screw member to align the pipes. The extending arm might limit the use of the apparatus only to applications where there is sufficient distance for the arm to extend between the two conduits to be joined.
U.S. Pat. No. 3,944,202 to Dearman discloses a clamping device for use in making mitred joints in pipe sections and U.S. Pat. No. 3,925,854 to McFadden discloses an alignment clamp. Both of these devices are similar to the Watson patent in that they both employ an extending arm and require sufficient distance for the arm to extend between the two conduits to be joined.
From the above prior art it can be seen that there is a need for a device which permits alignment of conduits having differing outside diameters and differing wall thicknesses and/or a curved portion adjacent the portion or part of the end portion to be joined.